When the producers of "Gangs of New York," the new Martin Scorsese blockbuster starring Leonardo DiCaprio, needed to figure out what music was appropriate for the movie's setting in 1800s New York City, they called the American Music Research Center at the ÀÖ²¥´«Ã½ at Boulder. So when the movie opens Dec. 20, CU-Boulder College of Music Professor Tom Riis, who provided the answers, will be in a theater listening closely and watching for a line in the end credits thanking the ÀÖ²¥´«Ã½ Libraries.